Two types of anchoring devices are known, each adapted to anchor in specific soils. The anchoring, whether on land or water, of buildings or structures can in fact be performed on loose soils or harder soils. Screw anchoring devices, having one or more attached helical discs welded on a rod, are therefore provided for loose soils. These screw anchors can thereby stabilize the structure to be anchored, once the first loose soil layer is thick enough.
Aside from this first problem related to the environment in which this type of device must be used, another drawback is that this type of screw anchoring device cannot be used in layers of hard soils. Self-drilling anchoring devices are provided in the case of these hard soils, in which devices the rod is provided at its end with a bit able to dig into the soil and whereof the dimension larger than the diameter of the rod makes it possible to create a cavity in which cement is injected to secure the anchoring with the ground. Such a self-drilling device does, however, have the drawback of not adapting to softer soils.
However, the anchoring structure can be made in a soil with varying hardness, formed from the surface by a first layer of loose soil, then a second monolithic layer. The use of one or the other of the devices mentioned above does not allow satisfactory anchoring of the structure. The first layer of loose soil has too small a thickness to stabilize a screw anchoring device, and the use of self-drilling anchoring is made impossible by the depth to which the second layer extends, the distance to the surface risking destabilizing the self-drilling anchoring.
Furthermore, the self-drilling capability of the anchoring devices used to date may be insufficient, in particular in certain underwater grounds of varied granulometry and mineral structure, compacted by water pressure, as well as certain ground on land consisting of clay and limestone or hydraulically compressed ground with a density similar to that of monolithic ground.